For television broadcasting, it is essential that videos, i.e., moving pictures are converted into television signals and transmitted, and a receiver receives these signals and performs reproduction processing to obtain the moving pictures and display them. In the case of sound signal which allows to treat a relation between time and sound pressure as one-dimensional one, instantaneous sound pressures (during a short time period) can be directly converted into electric signals. On the other hand, in the case of moving picture, if it is partitioned into still pictures at short time intervals, each still picture is planar, that is, two-dimensional information and therefore it is necessary to, prior to the conversion into signals, make their planes one-dimensional by scanning, so that the plane can be treated as a plurality of scan lines. Scan methods for obtaining a plurality of scan lines from pictures includes non-interlace scanning and interlaced scanning. Non-interlace scanning is a method in which all of the scan lines on a frame (a screen) are sequentially scanned from top to bottom to display a video image, and interlaced scanning is a method in which every other scan line is scanned.
When the display performance of a display device is not so high, non-interlace scanning causes flicker on screen due to the increase of the time difference between the top and the bottom of the scanning. Therefore, interlaced scanning is mainly employed in the conventional television broadcasting. In the NTSC system which is known as a common television system, assuming that one frame (screen) consists of 525 scan lines, two kinds of scanning, scanning for odd lines and scanning for even lines are performed, which means that two fields are scanned.
If the display device has a high display performance, however, the flicker on screen can be reduced by means of non-interlace scanning. Generally, a number of display times per second for a non-interlace scanning type computer display is approximately a double of the number of display times per second for an interlace scanning type one. Therefore, non-interlace scanning has captured much of the spotlight in the field of high-definition television or the like because it enables superior picture quality and high affinity for CG (computer graphics) or the like.
On the other hand, when moving pictures are digitized to be recorded and transmitted or received as digital data, the digitized data is generally treated as compressed code. As standardized moving picture compression technique, most common is MPEG (Moving Picture Experts Group), which is described in Latest Manual of MPEG (Ascii Co., Ltd, First Edition, published on Aug. 1, 1994) and Practical Manual of MPEG (Ascii Co., Ltd, First Edition, Published by (Nov. 1, 1995). These books also refer to the well-known transmission and reception methods for video data and video data reproducing apparatuses on the basis of MPEG standard.
In the prior art, techniques for transmitting and receiving video data based on MPEG standard have been established on the assumption that video data based on interlaced scanning is exclusively used because interlaced scanning is common in television broadcasting as described above. On the other hand, in the case of using videos based on non-interlace scanning, developments and the like have been developed on the assumption that video data subjected to non-interlace scanning is exclusively used.
The following description is on the conventional transmission and reception of video data using video image subjected to interlaced scanning which is common in television broadcasting or the like. As a first example of the prior art technique, a system for providing digital television broadcasting is described.
FIG. 29 is a diagram illustrating a structure of the data transmitted by the method of transmitting and receiving video data according to the first example of the prior art. As shown in the figure, video data of Program Number 1, video data of Program Number 3, and service information such as NIT (Network Information Table), PMT (Program Map Table), EIT (Event Information Table) are multiplexed on a packet basis within a band whose center is at a receive frequency of 12.568 GHz. In digital data transmission based on MPEG standard, since a plurality of programs (which correspond to channels in normal analog broadcasting) can be multiplexed and transmitted, the above-described pieces of service information are used to select a desired broadcast program in a desired program from the multiplexed transmission data, and these pieces of service information are thus multiplexed with the data to be transmitted.
Although the data structure of these packets and the standards on multiplexing of the packets are defined in detail in MPEG, here a description is given only of the portions particularly related.
Reference numeral 11 designates a packet of video data of Program Number 1 (channel 1). The packet identifier PID as the header is defined as 0x91 so that this packet can be identified as the packet of the video data of Program Number 1. Reference numeral 12 designates a packet of video data of Program Number 3 (channel 3). The packet identifier PID as the header is defined as 0x93 so that this packet can be identified as the packet of the video data of Program Number 3.
Reference numerals 13 to 15 designate packets of service information. Reference numeral 13 designates NIT (Network Information Table) packet which defines respective frequencies on which the video data of Program Number 1 and that of Program Number 3 are transmitted. This example shows that both the video data of Program Number 1 and that of Program Number 3 are multiplexed in the band of 12.568 GHz. Reference numeral 14 designates a PMT (program map table) packet. This example shows that the video data of Program Number 1 is included in a packet whose packet identifier is 0x91, the video data of Program Number 3 is included in a packet whose packet identifier is 0x93. Reference numeral 15 designates an EIT (event information table) packet. This example shows that in Program Number 1, "Baseball 1" will be aired from 19:00 to 20:00, "Quiz" from 20:00 to 21:00, and "Foreign film" from 21:00, and that in Program Number 3, "Baseball 1" will be aired from 19:00 to 20:00, "Soccer" from 20:00 to 21:00, "Baseball 2" from 21:00 to 22:00, and "News" from 22:00.
FIG. 30 is a diagram illustrating a prior art method of transmitting video data. Referring to the figure, numeral 100 designates a video data transmitting apparatus which is at a transmitting end, and numeral 200 designates a video data reproducing apparatus which is at a receiving end. In the video data transmitting apparatus 100, reference numeral 22 designates a video data storage unit for storing interlaced scanning type video data. Numeral 24 designates a multiplexing unit for multiplexing interlaced scanning type video data and the information relative to the data. Numeral 25 designates a transmitting unit for transmitting the signals multiplexed by the multiplexing unit 24. In the video data reproducing apparatus 200, reference numeral 1 designates a receiving unit for receiving the transmitted multiplexed signal, i.e., the signal shown in FIG. 22 consisting of the video data of Program Number 1, the video data of Program Number 3, NIT, PMT, and EIT. Reference numeral 2 designates a separating unit for separating the multiplexed signals received by the receiving unit 1, numeral 6 designates a program selecting unit for accepting selection operation of broadcast program from viewer and informing the receiving unit 1 and the separating unit 2 of the selected broadcast program. As the program selecting unit 6, widely-used popular selector may be employed such as a remote controller for selecting television program, channel buttons of a television receiver or a mouse of a personal computer. Reference numeral 4 designates an interlaced scanning type video decoding unit for decoding interlaced scanning type video data separated by the separating unit 2 and outputting the decoded data as a video signal.
Common video data reproducing apparatus further requires, other than the above, various components such as a decoding unit for decoding audio data. However, since these are not directly related to the present invention, they are not described for the sake of simplicity of explanation.
Next, the operations of the prior art video data transmitting apparatus and the prior art video data reproducing apparatus will be described.
Initially, in the video data transmitting apparatus 100, the multiplexing unit 24 multiplexes the interlaced scanning type video data of Program Number 1 and that of Program Number 3, and NIT, PMT, and EIT as the service information in packets of predetermined bit lengths as shown in FIG. 29, followed by the transmission from the transmitting unit 25.
The transmitted multiplexed signal is sent through a transmission medium such as electric wave or cable to viewer's reproducing apparatus where the viewer can utilize the signal. In the video data reproducing apparatus 200, video data is reproduced as follows.
First of all, the program selecting unit 6 accepts selection operation of broadcast program from viewer and informs the receiving unit 1 of the broadcast program designated according to the selection. This designation may be done directly by switching or inputting a numerical value as in the case of designating channel at a normal television receiver, and the selection may be carried out through a visual interface such as a program table which will be later described.
The receiving unit 1 receives a signal of a frequency on which the video data of the designated broadcast program (Program Number) is transmitted. Since a transmission signal of any receive frequency is multiplexed with an NIT of the same contents to be transmitted, the receiving unit 1 recognizes, from the contents described in the NIT, on which receive frequency the video data of the designated Program Number is transmitted, to perform selection of receive frequency.
The separating unit 2 separates video data from the information received by the receiving unit 1, according to the program selecting unit 6. More specifically, if the program selecting unit 6 instructs to reproduce the data of Program Number 1, the separating unit recognizes that the packet identifier PID of the video data of Program Number 1 is 0x91 from the contents of the PMT, and extracts a packet whose packet identifier PID is 0x91, and transmits it to the next stage. If it is instructed to reproduce the data of Program Number 3, as in the above case, the separating unit recognizes that the packet identifier PID of the video data of Program Number 3 is 0x93 from the contents of the PMT, extracts a packet whose packet identifier PID is 0x93, and transmits it to the next stage.
Thereby, the target video data is processed to reproduce a desired video. The interlaced scanning type video decoding unit 4 decodes the video data separated by the separating unit 2 in interlaced scanning mode to output it as a video signal, and the video display unit 8 receives the video signal output from the interlaced scanning type video decoding unit 4 as an input and displays a video image corresponding to the input signal on the screen.
FIG. 31 illustrates a program guide which is displayed on the screen of the conventional video data reproducing apparatus which performs display of the program guide. The conventional video data reproducing apparatus for performing display of the program guide processes the information of the EIT (event information table) in FIG. 29 and displays it on a screen in a form which is visually accessible to viewer, and the viewer views the program guide displayed on screen and selects a desired broadcast program using cursor, remote control key, or the like.
Next, a description is given of a second example of the prior art technology which is a system for providing plural types of services, for example, two types of services comprising digital television broadcasting and mosaic broadcasting. FIGS. 33 are diagrams for explaining these types of services. FIG. 33(a) illustrates digital television broadcasting which displays one program on one screen like the normal television broadcasting. FIG. 33(b) illustrates mosaic broadcasting which obtains unique effects by splitting the screen and displaying different video images in the resultant respective blocks. In this example, information for identifying the types of the services has to be transmitted, for comparison with the first example.
FIG. 32 is a diagram showing the structures of the data transmitted by the video data transmission method according to the second example of the prior art technique. Similarly as in the first example, the video data of Program Number 1 and that of Program Number 3, and NIT (network information table), PMT (program map table), and EIT (event information table) as the service information are multiplexed on a packet basis within a frequency band whose center is at a receive frequency of 12.568 GHz. In the present example, SDT (Service Description Table) is also multiplexed on a packet basis.
Referring to FIG. 32, the data structures of the video data portions 11 and 12, and the structures of the PMT 14 and EIT 15 among as the service information are identical to those in the first example. In this present example, the NIT includes the information about service types for the respective Program Numbers, and the SDT 16 includes information about service types and service names for the respective Program Numbers.
Also in the second example, the structures of the transmitting apparatus and the receiving apparatus are identical to those in the first example, and thus FIG. 30 is used for describing them.
A description is given of the operations of the video data transmitting apparatus 100 and the video data receiving apparatus 200. Initially, formation and transmission of multiplexed signals are performed by the video data transmitting apparatus 100 in the same manner as in the first example, and the multiplexed signal as shown in FIG. 32 is received by the video data reproducing apparatus 200. In the video data reproducing apparatus 200, reproduction is performed in the following steps: when separating video data to transmit the same, the separating unit 2 obtains the information of the service type from the service information NIT or SDT and transmits the information to the interlaced scanning type video decoding unit 4; the interlaced scanning type video decoding unit 4 performs decoding processing dependent on whether that service type is digital broadcasting or mosaic broadcasting. The operations other than the above one are the same as those of the first example and therefore will not be described.
Although the first and second examples exclusively handle interlaced scanning type video data, non-interlace scanning type video data may be handled in the same manner as described when the video data transmitting apparatus is configured to form and transmit multiplexed signals using non-interlace scanning type data and the video data reproducing apparatus is configured to have a non-interlace scanning type decoding unit in place of the interlaced scanning type decoding unit.
As described above, although interlaced scanning is popular as a method for scanning pictures, non-interlace scanning is also expected to be used increasingly in the future, and it is even thought that both interlaced scanning type video data and non-interlace scanning type video data might be supplied to a same digital broadcasting system. Therefore, it can be predicted that demands for a video reproducing apparatus capable of reproducing videos according to each of the scan methods would increase.
In the prior art video data reproducing apparatus described above, when non-interlace scanning type video data is multiplexed and transmitted, the interlaced scanning type video decoding unit cannot perform decoding correctly, whereby correct video signals cannot be output.
Even when pieces of data of the both scanning types are mixedly supplied to the foregoing reproducing apparatus, problems do not occur as long as the interlaced scanning type data only is reproduced. However, since it is difficult to see, from a program guide displayed by the prior art video data reproducing apparatus, whether the broadcast program is of a non-interlaced scanning type or of an interlaced scanning type, as shown in FIG. 31, viewer might erroneously select a broadcast program whose scanning type is different from that of the video decoding unit of the video data reproducing apparatus. In the above-described video data reproducing apparatus of FIG. 30 which includes the interlaced scanning type video decoding unit only, when viewer selects a broadcast program in a non-interlace scanning type program, the video data cannot be reproduced correctly and distorted video images are output.
The foregoing problems are common in the first and second examples, and the systems configured to correspond only to the non-interlace scanning type video data cannot handle the interlaced scanning type video data similarly.
Thus, in the prior art video data transmission method and the video data transmitting apparatus, since a multiplexed signal is transmitted including only one of the interlaced scanning type video data and the non-interlace scanning type video data, the degree of freedom in programing of television broadcasting programs is limited.
Further, as described above, since the prior art video data reproducing apparatus includes only one of the interlaced scanning type video decoding unit which decodes interlaced scanning type video data and the non-interlace scanning type video decoding unit which decodes non-interlace scanning type video data, the program whose scan method is different from that of the video decoding unit provided therein cannot be reproduced correctly.
Furthermore, since the prior art video data reproducing apparatus for performing display of the program guide displays on the screen a program guide which makes it difficult to know whether each broadcast program is of a non-interlace scanning type or of an interlaced scanning type, viewer tends to erroneously select a broadcast program of a scan method by which the video data reproducing apparatus cannot perform correct reproduction.
To solve the above problems, provided is the present invention which has an object to provide a video data transmitting method in which both interlaced scanning type video data and non-interlace scanning type video data can be transmitted so that the receiving end can reproduce data of both scanning types correctly, resulting in improved degree of freedom in programing of broadcast programs to be transmitted.
The present invention has another object to provide a video data reproducing apparatus which receives a signal transmitted by the method of transmitting video data in which both interlaced scanning type video data and non-interlace scanning type video data are transmitted, reproduces both the interlaced scanning type video data and the non-interlace scanning type video data correctly, and displays the reproduced data.
The present invention has still further object to provide a video data reproducing apparatus capable of confirming the scan method for a broadcast program to be selected when reproducing one of plural broadcast programs transmitted according to the video data transmission method in which both the interlaced scanning type video data and the non-interlace scanning type video data are transmitted, thereby preventing incorrect selection.